History of humanity: scientific and cultural development, v. II: From the third millennium to the seventh century B.C.
Towards 3100 bc, at the start of the period dealt with in this volume, humanity already had a past which stretched back to some two and a half million years, and it had gone through 99.5 per cent of its existence from the emergence of the first being who can be classified under the genus Homo to the present day.
We shall not return here to the distinction usually drawn between the prehistoric age – the period before the appearance of writing – and the historical period in the strict sense of the word, or to the vast, almost unimaginable, duration of this most ancient of human adventures. The reader will find further details on this subject in the General Introduction to Volume I. It should nevertheless be pointed out that Volume I, in spite of the length of time it covers, restricts itself to the period when all populations were still ignorant of writing, and prehistory was still far from nearing its end. In the two and a half thousand years covered by this volume, the knowledge of writing was in fact limited to a handful of regions, and the great majority of populations were still in the prehistoric stage.